President Donald Trump has said Iran will pay a big price after the US embassy in Baghdad's attack, BTA quoted France Press as saying.

Mr Trump tweeted: “The U.S. Embassy in Iraq is, & has been for hours, SAFE! Many of our great Warfighters, together with the most lethal military equipment in the world, was immediately rushed to the site. Thank you to the President & Prime Minister of Iraq for their rapid response upon request.”, The Independent reported.

“Iran will be held fully responsible for lives lost, or damage incurred, at any of our facilities. They will pay a very BIG PRICE! This is not a Warning, it is a Threat. Happy New Year!”, Donald Trump wrote in a tweet.

However, Iran's Supreme Leader Ayatollah Ali Khamenei responded by saying the US "can't do a damn thing".

“If the Islamic Republic decides to challenge & fight, it will do so unequivocally. We’re not after wars, but we strongly defend the Iranian nation’s interests, dignity, & glory.

If anyone threatens that, we will unhesitatingly confront & strike them.”